LEIGH SALES, PRESENTER: Secrets from one of the most prestigious schools in the world have been prised open over the past week.

A culture of bullying, sex abuse and cover-ups at Geelong Grammar, spanning almost 50 years, has been revealed at the Royal Commission into child sex abuse.

It flourished in the 80s and 90s under the leadership of headmaster John Lewis. He's regarded as one of the world's finest educators and was recruited from Geelong Grammar to Eton. There he was the headmaster to Prince William and Prince Harry.

But the royal commission has heard that John Lewis didn't go to the police when he was told of abuse allegations against at least two of his staff.

Jessica Longbottom reports.

(Montage of testimony at Royal Commission into Institutional Responses to Child Sexual Abuse)

STATEMENT BY PHILIP CONSTABLE (read): I was sexually abused by Dennis between 1956 and 1958...

TERRY GREY, SEXUAL ABUSE VICTIM: ...never reported the abuse to the school authorities because I didn't think I would be believed.

"BIW", SEXUAL ABUSE VICTIM: I knew other children would be abused 'cause no-one would listen to me.

(Montage ends)

LUKE BENSON, SEXUAL ABUSE VICTIM: I was left with so many questions of: how did this happen? Why did this happen? Is it a safe place now for kids or not?

JESSICA LONGBOTTOM, REPORTER: Founded in 1855, Geelong Grammar School is the alma mater of the rich and famous, from Prince Charles to Rupert Murdoch.

But these school grounds have also been the home of sex abusers and their victims.

JOHN LEWIS, PRINCIPAL, ETON: I swear by almighty God...

Today after a week of evidence, one of the school's most celebrated principals apologised for what happened when he was in charge.

JOHN LEWIS: Of course, I regret most of all the fact that some pupils and parents, sometimes in the course of school careers that were otherwise happy and successful, suffered hurt and embarrassment to which they ought never to have been subjected.

I am very sorry for that.

LUKE BENSON: I know every year was a challenge to keep me at Geelong and paying the fees, but it was a massive source of pride.

JESSICA LONGBOTTOM: Luke Benson boarded at Geelong Grammar's Highton campus for two years from 1988.

He had a close relationship with many teachers, including boarding assistant Phillippe Trutmann.

LUKE BENSON: Absolutely nothing untoward stands out in my mind, but I remember back rubs and I remember, um... as I said, privileges after hours, things that were outside the rules that were acceptable or encouraged for me.

JESSICA LONGBOTTOM: It wasn't until he received a phone call from police 10 years ago that his memories of school were turned upside down.

Trutmann had confessed to abusing Luke up to 40 times. Luke believes much of it happened while he was asleep.

LUKE BENSON: I thought it was a mistake at first. And then it didn't take long to realise it probably wasn't a mistake and...

It's with me every day. It's not a... It's not something I don't think about. It's something I probably obsess about and try and fill in the gaps of what happened and try and work out what might have happened.

JESSICA LONGBOTTOM: Luke wasn't the first of Trutmann's victims - and he wasn't to be the last.

Around the time Luke was assaulted, another student told staff about being abused at Highton.

The student was expelled and there was no investigation, despite evidence a potential paedophile was operating in the boarding house.

The decision was approved by then headmaster John Lewis.

JOHN LEWIS (1994): I just happened to have become a boarding school person. Boarding does offer growing young people a very special opportunity in terms of their own personal growth and development

JESSICA LONGBOTTOM: Lewis was at the helm of Geelong Grammar for 14 years from 1980. A talented rugby player and proud New Zealander, the classical scholar has been described as "a charismatic yet formidable character."

After Geelong Grammar, he went on to lead one of the most famous schools in the world, Eton, where he was headmaster to Prince William and Prince Harry.

(Footage of John Lewis at Eton with Prince Charles, Diana, Princess of Wales, Prince William and Prince Harry)

This video shows him in 1995, showing a young Duke of Cambridge around on his first day at school.

(Footage ends)

Today he was being asked why he didn't investigate numerous reports of abuse when he was headmaster of Geelong Grammar.

JOHN LEWIS: Few of the matters involving alleged sexual abuse were easy to deal with at the time. If some of them seem now clearer in retrospect than they did then, that is at least partly because I have subsequently become aware of things of which I knew nothing then.

JESSICA LONGBOTTOM: Phillipe Trutmann was convicted of molesting at least 41 students over 10 years. But he wasn't the only paedophile that worked at Geelong Grammar under John Lewis.

"GEORGE": John Lewis is an exceptional person. He's very well achieved in every area of his life that he's ever had any endeavour in.

I think he missed an opportunity to protect a vulnerable student.

JESSICA LONGBOTTOM: "George," as we'll call him, was five years old when he started at Geelong Grammar in the early 70s.

He alleges when he was 15, housemaster Jonathan Harvey gave him a massage on multiple occasions when he stayed at his house - in one instance touching his genitals.

"GEORGE": He listened and took notes and he said that, you know, neither of us should speak to anybody until he had had a chance to resolve the issues and talk to the master concerned.

JESSICA LONGBOTTOM: Lewis spoke with Harvey, who denied the allegations.

JOHN LEWIS: I was immediately faced, as I found it, with a dilemma.

I had no ground or reason to disbelieve the allegations. On the other hand, I... found it very unlikely.

But Mr Lewis, you had an allegation by someone you described as "a senior and responsible student" that a teacher on your staff had tried to have sex with him on more than one occasion?

JOHN LEWIS: Yes. I'd also been in receipt of a statement - informal - from a senior and responsible member of staff.

JESSICA LONGBOTTOM: Lewis didn't take the complaints any further.

There were other warning signs about Jonathan Harvey where Lewis failed to act. After George's report in 1982, letters show John Lewis continued to permit Harvey to have students stay at his house. In 1991, Lewis warned Harvey he'd received even more complaints about his relationships with students. Despite this, he allowed him to stay on staff.

JOHN LEWIS: You don't want to provoke a hornet's nest until you're much ca... until you're much surer of your ground. I do not believe at that time that there was a requirement automatically to notify the police.

JESSICA LONGBOTTOM: The allegations Lewis failed to protect students tarnishes the record of a man known as an accomplished principal and that of a school that appears to have been concerned about its reputation over the safety of its students.

I know everyone regrets that this happened and I think everyone acknowledges a lot of mistakes were made. And I try not to think about whether it was preventable.